UL/LI issues

I've noticed that if some of my user's don't do such a good job using <UL> tags for all of their list items <LI> that the editor has a very very difficult time rendering the page and will do some really wacky things trying to make the page render. This wasn't the case for v2, but v3 is creating a huge mess on some of these pages.

Has anyone else seen this issue? Obviously the best solution is to have well formatted HTML, but the changes between versions are VERY significant.